ASTM A967 vs. AMS 2700? Which is the right passivation spec?

My customer wants to put A380-96 on his print for standard passivation, but my plater tells me that he passivates to A967-96. What should I tell my customer?

2nd question, if I ask for standard passivation on imported product, what ASTM spec do you think I will get?

Thank you

Gene Prehatney- Champlin, Minnesota

(2003)

A. First question: The current ASTM versions are A380-99e1 "Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems" and A967-01e1 "Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts".

It is relatively easy to modify a passivation process to satisfy ASTM A380 [link is to the practice at TechStreet]
, andASTM A967 [link by ed. to spec at TechStreet]
, andQQ-P-35 [link is to free spec at Defense Logistics Agency, dla.mil]andAMS2700 [link by ed. to spec at TechStreet] (primarily, a little paperwork). Have the plater do so, and then certify to multiple standards. (Lee Kremer has pointed out that A380 is not a Specification, only a Practice).

Second question: A guessing game? "Standard passivation" is meaningless unless the standard is specified.

Ken Vlach- Goleta, California

Finishing.com honored Ken for his countless carefully
researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work
which the finishing world continues to benefit from.

(2003)

A. As Ken says, ASTM A380 should not be used as a passivation specification, and QQ-P-35 has been canceled. The 3 consensus specifications used at this time, and that should be used for all specifications of passivation are:

ASTM F86 [link by ed. to spec at TechStreet]
for Orthopedic implants,AMS2700 [link by ed. to spec at TechStreet]for Aerospace,ASTM A967 [link by ed. to spec at TechStreet]
for all other applications.
There are other in-house specifications for some companies.

A-380 has a lot of excellent recommendations on general cleaning etc. of stainless steel, but should never be used as a passivation spec.

AMS QQ-P-35 is being canceled in favor of AMS 2700 (at the moment it is version B)

You should never ask for "standard passivation" on imports. Always specify exactly what you want-- e.g., ASTM A967 01e, Citric 4 or AMS 2700B Nitric 1. If you do not specify, they can use whatever they want, even ways that are not in any of the specifications! What is standard to you may not be standard to them.

December 17, 2008 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I am struggling to understand which spec to use for passivation. Is there any clear direction or is it optional? Thanks for reading.

John Wilt Engineer - Cambridge, Massachusetts

December 19, 2008

A. The "right" spec is the one that your customer requires. ASTM A967 [link by ed. to spec at TechStreet]
is certainly more lax regarding passivation verification testing, which can be a good thing or a bad thing.
AMS2700 [link by ed. to spec at TechStreet] requires both solution and per-lot corrosion resistance testing.

Since you're considering an AMS spec, I assume you have aerospace customers. If not, I would stick with ASTM.

Terry Lycans Aerospace - Dayton, Ohio, USA

December 19, 2008

A. One of the differences is in the definition of 'a lot' for testing purposes. ASTM A 967 uses the same definition as did the old Federal Specification,
QQ-P-35.html, which allowed one to consider all production of similar material done in 24 hours to be a single lot. AMS 2700 considers different parts, or the same part made at different times, to be different lots (with the exception for parts with the legacy QQ-P-35 called out, when you can use the older definition.) You can guess the increase in the amount of testing involved.

There are other differences- ASTM A967 allows the use of any mix of nitric and water, so long as you show it works (Nitric 5 solution). The ASTM doesn't default to the nitric acid formulations, as AMS 2700 does. AMS 2700 has an iron concentration maximum, absent from ASTM A 967. AMS 2700 exempts 440C from testing. And there are other differences.

We design our own parts, and do our own passivation in house, and hence prefer the testing requirements of ASTM A967. If you're having it done for you, the testing is someone else's problem, so you might consider AMS 2700.

Lee Gearhartmetallurgist

January 20, 2009

Terry/Lee, Thanks for your responses. They were helpful.

John Wilt [returning]- Cambridge, Massachusetts

October 21, 2009 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Can you please tell me the differences between the passivation processes AMS2700 [link by ed. to spec at TechStreet]C vs ASTM A967 [link by ed. to spec at TechStreet]
. I have a note requirement for the ASTM A967, Type 6 or 7 requirement on some parts and the parts were passivated to the AMS2700C, Method 1, Type 6 requirement.

Ted Nance customer - San Diego, California

October 23, 2009

A. The two standards are essentially equivalent. Both contain a carryover of QQ-P-35C with the addition of the more recently developed citric acid based process. The AMS standard is used by the aerospace industry while the ASTM standard is used by generally everyone else.

QQ-P-35B contained six nitric acid bath Types. The C revision removed four of those and added two, leaving as options, Types II, VI, VII, and VIII. A967 renumbers those to 1 through 4 (there is no such thing as A967 Type 6 or 7) while 2700 restores the missing four for a total of eight Types.

A. A967 is a standard covering treatments to passivate stainless steel (regardless of what it will be used for) and then test methods to show that it was passivated.

F86 refers to surgical implants of any metallic alloy, and basically just says "do whatever treatment is applicable and appropriate to ensure corrosion resistance".

And then there's F1089, which is test methods to show stainless steel surgical instruments have been passivated.

As far as the stainless steel passivation process itself, you're pretty much always going to work your way back to A967. But if it's a medical instrument or implant, then you're also going to have to show the appropriate tribute to an F standard.

Q. I have an engineering drawing that calls out passivation IAW AMS 2700, Method 2, Type 2. In reading through the specification I believe the drawing is incorrect. It appears that the types are associated with method 1, not method 2. Is this correct?

Tom Blauser - Dayton, Ohio, USA

March 7, 2017

A. Tom,
Correct. Method 1 is subdivided into 8 Types (corresponding to the types in old QQ-P-35) while Method 2 is not subdivided.

So the question is, did they mean "Method 1 Type 2" or "Method 2 OR Method 1 Type 2"

I ran my validation at the nominal settings (8, 130 °F and 17.5 min) and the auditor is asking me why we did not run the validation in the process limits. I replied that the parameters are in compliance with standard A967 but he's telling that we don't have objective evidence to support the validation since A967 defines minimum requirements that could be insufficient to my process. In simple terms, he's saying that given 2 SS surfaces which have different concentrations of free iron, the chemical reaction will take longer in the surface with more free iron. That makes sense.
Based on the previous information, the concern is regarding the minimum requirements in A967. Do the parameters in A967 cover any worst case scenario? If so, how could I support that statement? I assume that A967 was developed running several extreme conditions but I've been looking for that information and couldn't find anything about it.
I really appreciate your collaboration.

Juan,
If you process parts within the parameter ranges given by ASTM A967 [link by ed. to spec at TechStreet]
, and one part per lot passes one of the listed test methods, then all you can say is you ran the parts in accordance with A967.

Determining the suitability of A967 for your specific parts is up to you, or requirements set by your customer. I.e., in some cases the best minimum time for your process may be longer than A967's stated minimum time. Some customers ask for the parts to pass salt spray testing longer than A967's required 2 hours, etc.

"Validation" as a term is not defined or used in A967 and means several different things depending on who you talk to. The best thing do to is ask the customer what they expect.

This auditor you are dealing with, what organization is he with? Your customer? What requirement or standard is he auditing you against, since clearly it is not A967?

Revision C of QQ-P-35 had some of the formulas taken out, so it had only types II, VI, VII, and VIII. ASTM A967 renumbered those to nitric 1 through 4, while AMS 2700 brought back the ones that had been removed and has types 1 through 8.

Both standards express the formulas as volume percent of nitric acid, though only 2700 actually mentions the nitric stock solution is 42 °Baumé/67 wt%. This is actually an oversight of A967 that will be corrected in the next revision.

Thank you for answering.
Indeed also my conclusion is that it is an omission.
In the ASTM A967-2013 and the nitric acid concentrations mentioned must be percentage by volume of a reagent of 67 wt.% nitric acid.

Jan Mulder [returning] - Hengelo, Overijssel, The netherlands

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